In the currently-used Cu interconnection film-forming process, a PVD-barrier film (for instance, PVD-Ti film or PVD-Ta film) and PVD-seed film (PVD-Cu film) are formed according to the through production process in vacuo (vacuum-in situ process) and subsequently a Cu-plating process and a CMP process are carried out. However, on or after the generation of the device node of 32 nm, the asymmetry and overhang observed for the wafer edge of a PVD film have become more and more conspicuous because of the recent micronization of the interconnection pattern and for this reason, the currently-used interconnection film-forming process suffers from a problem such that voids are generated in the resulting interconnection film during the plating process.
In this connection, the term “PVD-barrier film” means a barrier film formed according to the PVD technique and the term “PVD-seed film” means a seed film formed according to the PVD technique. The PVD (CVD)-Cu film, the ALD-barrier film and the CVD (ALD)-Co film appearing in the following description mean the respective films formed according to the PVD, CVD and ALD techniques, respectively.
If a PVD-seed film 103 (PVD-Cu film) is formed on a barrier film 102 provided on a substrate 101, which is provided thereon with holes each having a diameter φ of 32 nm and trenches, as shown in, for instance, FIGS. 1(a) and 1(b), the following problems would arise: The openings of, for instance, the holes or trenches are narrowed or degraded due to the overhang (the portion indicated by A) observed at the upper portions of the holes or trenches; and when filling up the interior of the holes or the like with a Cu film 104 in the subsequent plating step, a plating solution cannot easily penetrate into the same and the adhesion between the Cu film and a barrier film is insufficient, and this in turn results in the sucking of the Cu film along with the filling up of the same with the Cu film and voids (the portion indicated by B) are thus generated within the resulting Cu film. Moreover, the following problem would likewise arise: As shown in FIGS. 1(c) and 1(d), any uniform and symmetrical PVD-seed film 103 cannot be formed on the side walls of the holes or the like (see the portion indicated by C), and voids (the portion indicated by D) are generated or formed within the Cu film 104 used for the filling up of the holes or the like during the subsequent plating step, because of the asymmetrical characteristics of this barrier film.
Since the barrier film formed according to the ALD and/or CVD techniques and the CVD-Cu film do not suffer from such problems as the occurrence of any asymmetry and the formation of overhang, it has been attempted to form a Cu interconnection film using these two processes (see, for instance, Patent Document 1 specified below). However, a problem likewise arises, in this case, such that the adhesion of the CVD-Cu film to the ALD-barrier film as a primary film therefor is insufficient and accordingly, voids are also generated within the Cu film. For this reason, this technique has not yet been put into practical use.
For example, as shown in FIGS. 2(a) and 2(b), if a TiN barrier film 202 is formed within the holes and trenches arranged or formed on a substrate 201 according to the ALD technique (ALD-TiN barrier film) and then the interior of the holes or the like are filled up with a CVD-Cu film 203, voids (the portion indicated by A) are generated in the Cu film thus formed. In this connection, FIG. 2(a) is an SEM micrograph illustrating a cross section of the substrate wherein the holes and trenches provided thereon are filled up with the CVD-Cu film 203, while FIG. 2(b) is a schematic diagram thereof.
There have been made attempts to use a Co thin film excellent in the coverage properties and having low resistance in order to eliminate the generation of any void in the Cu film due to the insufficiency of the adhesion between the CVD-Cu film and the ALD-barrier film serving as the primary film therefor as has been discussed above and to improve the barrier properties and/or the adhesion and for this reason, it would be an urgent necessity to develop a Co film forming technique while using the CVD or ALD technique. Regarding the Co film, there has also been a growing demand for the development of a Co film having excellent coverage properties in not only the field of the Cu interconnection film, but also the field of the silicide layer and the cap layer.
Contrary to this, in the case of the conventional Co film produced according to the CVD technique while using an organometal material containing Co and an amine (see, for instance, Patent Document 2 specified below), various problems arise such that this technique requires a long Co nucleus-growing time on the order of 20 minutes, the growth rate of Co nuclei is likewise slow on the order of 1 nm/min and the resulting Co film has a high concentration of C as an impurity, which may reach 30%.